1. Field of the Invention
The present invention relates to a clamping assembly for securing a pair of casings in alignment with one another and in particular to an arrangement which utilizes tapered or wedge-shaped keys to align and secure a pair of casings forming a pressure vessel such as encountered in a steam turbine assembly.
2. Description of the Prior Art
In the typical steam turbine assembly, a plurality of steam injection or finger nozzles project into the turbine from the steam chest. As is well known in the art, the distal end of each of the finger nozzles is axially aligned with the blades of the turbine wheel and is secured at a fixed distance from the wheel determined by the various design criteria of the turbine.
Each of the finger nozzles is secured to the steam chest about one of its associated steam ports and extends through a common port into the turbine casing. Thus, it can readily be seen why the steam chest casing must be secured to the turbine casing in a fashion accommodating relatively close alignment between the steam ports in the casings to insure proper spacing and alignment between the finger nozzles and the blades of the turbine wheel.
The partial cross-sectional view shown in FIG. 6 entitled "Prior Art" illustrates one type of aligning device which has commonly been used in the past. As shown in FIG. 6, the steam chest casing 1 is initially positioned on the turbine causing 2 with the finger nozzles 3 projecting into the turbine casing to direct the steam flow into the blades 4 as indicated by the arrow 5. Then, by adjusting a plurality of machine or jacking screws 6 disposed on the opposite sides of the casing, this arrangement enables a workman to adjust the alignment of the steam ports 7 and 8 to obtain the desired axial spacing "S" between the finger nozzles 3 and the blades of the turbine wheel. Once this spacing is established, the casings are secured together by a plurality of holding bolts 9 in the usual manner.
While the foregoing arrangement has been for the most part satisfactory, the jacking screws 6 can only be used to align the casings. As such, they contribute little if anything to the integrity of the connection between the casings or, more specifically, to the distribution of the high pressure steam loads between the two casings after the turbine is put in service.
In addition to the foregoing, the prior art also includes a variety of clamping arrangments for aligning a pair of housings. For example, U.S. Pat. No. 3,365,123 shows a wedge-type adjustable clamp for securing a motor on a blower housing, and U.S. Pat. No. 4,380,405 discloses an arrangement wherein a plurality of slide keys are used to mount a head flange on the casing of a centrifugal compressor. While both of those patents show the use of clamping arrangements, neither teaches the use of a plurality of wedge keys to align a steam chest casing on a turbine casing which also enhances the distribution of high pressure loads throughout both casings.